With respect to the production of α-hydroxyamide by microorganisms, method for producing corresponding amides from lactonitrile, hydroxyacetonitrile, α-hydroxy methylthiobutyronitrile, and such, using microorganisms belonging to the genus Bacillus, Bacteridium, Micrococcus, or Brevibacterium (see Examined Published Japanese Patent Application No. (JP-B) Sho 62-21519) are known in the art. In addition, method for producing mandelamide from cyanohydrin (see Unexamined Published Japanese Patent Application No. (JP-A) Hei 4-222591; JP-A Hei 8-89267) is also known in the art.
However, enzymes having nitrile hydratase activity, which possess the ability of converting nitrile compounds to amide compounds, have a problem to readily lose their enzymatic activities due to the presence of nitrile compounds or amide compounds that are the starting materials or the products, respectively. If the concentration of nitrile compound is raised in order to increase the rate of amidation within a reaction, the nitrile hydratase is readily inactivated in a short period of time, and thus it is hard to obtain amide compounds as the reaction product in a desired period of time. Furthermore, the nitrile hydratase is also readily inactivated by amide compounds, i.e. the products, and thus it is difficult to obtain amide compounds with a high concentration.
Furthermore, in varying degree depending on the type of compound, α-hydroxynitrile has been known to get partially decomposed to the corresponding aldehyde and hydrocyanic acid in a polar solvent (see V. Okano et al., J. Am. Chem. Soc., Vol. 98, 4201 (1976)). In general, aldehydes have the characteristic to bind to proteins to inactivate the enzymatic activity (see Chemical Modification of Proteins, G. E. Means et al., Holden-Day, 125(1971)). Further, like aldehyde, hydrocyanic acid (cyanide) has also an inhibitorily effect on many enzymes. Thus, aldehyde and cyanide produced from of α-hydroxynitrile as the starting material has been the cause of decreased enzymatic activity. Due to the inactivation of the enzyme in a short period of time in the enzymatic hydration or hydrolysis of α-hydroxynitrile, it has been difficult to obtain a high concentration of α-hydroxyamide with high productivity.
To prevent the decrease in the enzymatic activity, various methods for increasing the enzymatic activity or for suppressing the decrease of enzymatic activity (inactivation) have been tested. Such attempts, for example, include:                Carrying out the reaction at a lower temperature ranging from the freezing point to 15° C. (JP-B Sho 56-38118);        continuously supplying the substrate with a lower concentration from multiple supply ports (JP-B Sho 57-1234);        treating the microorganism or processed product thereof with an organic solvent (JP-A Hei 5-308980);        carrying out the reaction in the presence of higher unsaturated fatty acid (JP-A Hei 7-265090);        crosslinking the cells of microorganism with glutaraldehyde and such (JP-A Hei 7-265091; and JP-A Hei 8-154691);        lowering the concentration of hydrocyanic acid contaminated in the nitrile compound by a chemical method, and then acting the nitrile hydratase with the nitrile compound (see JP-A Hei 11-123098);        stabilizing the enzymatic activity for a long period of time by the presence of sulfite ion, acid sulfite ion or dithionite ion (see JP-A Hei 8-89267); and        adding aldehyde (see JP-A Hei 4-222591).        
None of these methods were sufficient enough for industrial applications. Although some of the methods were effective, there was room for economical or practical improvement. For example, the above-mentioned method of adding aldehyde requires a large quantity of aldehyde, which is 1 to 5 times molar excess to the cyanohydrin (i.e. the starting material), and thus was far from providing an economical solution. Similarly, the method wherein sulfite ion, acid sulfite ion or dithionite ion are added requires equivalent or larger amounts of ions to the starting material, and thus was not practical.